The present invention relates to inductive battery chargers, and more particularly, to a composite core that controls the temperature of an inductively coupled charge probe used to charge the propulsion batteries of electric vehicles.
The assignee of the present invention designs, develops and manufactures inductive charging systems for use in charging electric batteries of electric vehicles, and the like. The charging system employs a charge port comprising secondary windings and core that form a secondary of a transformer installed in the electric vehicle, and a charge coupler or probe comprising a primary winding and a core that form a primary of a transformer that is coupled to a power source and which is inserted into the charge port to charge the vehicle batteries. Charging of the batteries is done at high frequency and at high charging rates. Consequently, there is a great deal of heat buildup in the charge probe. The probe must be removed from the charge port by a user once charging is completed, and the temperature of the probe is a concern.
Four different approaches may be used to implement thermal management of inductive charge coupler port temperatures. The first approach is to rely on conduction of heat from the primary winding and core across an air gap interface to on-board heat exchangers having cooling air circulated by charge port fans. This approach works for systems operating from about 6 kw to 10 kw charging rates. The second approach is to route chilled air from off-board refrigeration unit through the coupler. This approach works for systems operating at charge rates from about 20 kw to 25 kw.
The third approach is to use a plastic heat exchanger that does not interact with the magnetic fields produced by the charging system. However, this approach has poor thermal transfer characteristics. The fourth approach is to use a metallic heat exchanger, that interacts with the magnetic field, resulting in a degree of proximity losses, depending on its location in the winding.
A discussion of metallic heat exchangers may be found in U.S. patent application Ser. No. 08/237,493, filed Apr. 27, 1994, entitled "Liquid Cooled Metallic , Inductive Probe for High Power Charging", assigned to the assignee of the present invention, which describes how to cool a winding of an inductive probe with a liquid fed plastic bladder, and how to interface a liquid fed metallic heat exchanger in a winding of an inductive probe, such that there is no interacting with the magnetic fields. U.S. patent application Ser. No. 08/237,494, filed Apr. 29, 1994, entitled "High Frequency Transformer Winding Having an Internally Liquid Cooled Winding", assigned to the assignee of the present invention, describes how to interface a liquid fed metallic heat exchanger in the winding of an inductive probe, and integrate this as a turn of the transformer winding such that there is no interaction of the heat exchanger with the magnetic fields. U.S. patent application Ser. No. 08/237,495, filed Apr. 29, 1994, entitled "Method of Cooling of Inductive Charge Magnetics Using Internal Heat Pipes", assigned to the assignee of the present invention, describes how to cool a winding of a charge port with a heat pipe. U.S. patent application Ser. No. 08/146,690, filed Nov. 2, 1993, entitled "Ducted Air-Cooled Secondary of Automotive Battery Charging Transformer", assigned to the assignee of the present invention, describes how to cool a winding of a charge port with a ducted air-cooled heat exchanger. The disadvantage of this approach is that the air cooled heat exchanger is not an integrated turn, that is, it only serves as a heat exchanger.
Therefore, it is an objective of the present invention to provide for a high power inductive battery charging apparatus employing a charge probe having an improved composite magnetic core. It is a further objective of the present invention to provide for a composite core that controls the temperature of an inductively coupled charge probe used in inductive battery charging apparatus to charge the propulsion batteries of electric vehicles.